This invention relates to color cathode ray tubes for use, for example, in color television receivers and more particularly to improvements in a magnet shield disposed within such a cathode ray tube.
It is well known that cathode ray tubes for use in color television receivers are provided with a magnetic shield for eliminating the effects upon the cathode ray tubes due to terrestrial magnetism and/or undesirable magnetic fields caused by the electric circuit of the associated television receiver. It is also well known that such a magnetic shield is disposed within the enclosed envelope of a cathode ray tube to make the resulting shielding effect greater. The magnetic shield disposed within the envelope is called an "internal magnetic shield" and is generally connected by welding to a shadow mask disposed in the envelope.
However, such a magnetic shield joined to the shadow mask results in an increase in the undesirable thermal deformation of the shadow mask. This is due to the fact that the magnetic shield impedes the heat dissipation from the shadow mask to the envelope, and more particularly to the funnel portion thereof. On the other hand, the shadow mask is coupled to the interior of the envelope through supporting means, and therefore the magnetic shield connected to the shadow mask increases loading on such supporting means, leading to the necessity of rendering the supporting means stronger. It is desirable to make the magnetic shield as light as possible in weight.